Preprints
There are 4725 Preprints listed.
Machine Learning Reveals the State of Intermittent Frictional Dynamics in a Sheared Granular Fault
Published: 2019-03-05
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Geophysics and Seismology, Geotechnical Engineering, Physical Sciences and Mathematics
The seismogenic plate boundaries are presumed to behave similarly to a densely packed granular medium, where fault and blocks systems rapidly rearrange the distribution of forces within themselves, as particles do in slowly sheared granular systems. We use machine learning and show that statistical features of velocity signals from individual particles in a simulated sheared granular fault [...]
Autogenic translation and concave bank deposition in meandering rivers
Published: 2019-03-02
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics, Sedimentology
Although it has long been recognized that deposition along meandering rivers is not restricted to convex banks, the consensus is that external forcing, that is, confinement by an erosion-resistant barrier, is necessary for significant concave-bank deposition to occur. Using a kinematic model of channel meandering and time-lapse satellite imagery from the Mamoré River in Bolivia, we show that [...]
Hydrodynamic control of gas-exchange velocity in small streams
Published: 2019-03-02
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Sciences, Fluid Dynamics, Hydraulic Engineering, Physical Sciences and Mathematics, Physics, Planetary Sciences
Gas exchange is a critical component of any biogeochemical mass balance model of dissolved gases in aquatic systems, yet the magnitude and drivers of spatial and temporal variations of air-water exchange rates in shallow streams are poorly understood. We investigated the relationships between gas exchange velocity of carbon dioxide and methane and flow hydraulics at different sections along a [...]
Zealandia’s Early Paleozoic sandstones: detrital mineralogy of the Greenland and Reefton Groups
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
New point counts of 13 Buller Terrane sandstones have been made. The results suggest a less quartzose and more lithic rich content of detrital sand grains in the Ordovician Greenland Group than indicated by an earlier published study (average Q:F:L = 58:16:26 and 23% matrix rather than 81:8:11 and 37% matrix). A low grade sedimentary-metasedimentary provenance is indicated. Detrital K-feldspar, [...]
Determining sources of placer minerals using U-Pb ages of detrital zircons: example of auriferous quartz pebble conglomerates in Otago and Southland, New Zealand
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
We have dated populations of detrital zircons in two Miocene gold-bearing quartz pebble conglomerates, one at St Bathans in Central Otago and one near Gore in Northern Southland. Both samples contain large numbers of Triassic-Permian zircon grains that indicate a source area dominated by Eastern Province Torlesse Composite Terrane protoliths. On the basis that the detrital quartz, zircon and gold [...]
Revised three-dimensional geometry of the platiniferous Hekeia Gabbro, Longwood Range, Southland
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
The Hekeia Gabbro in the Longwood Range of Southland is prospective for platinum group element mineralisation. Recently acquired geological and isotopic data, combined with reinterpreted aeromagnetic data, provide new constraints on the three dimensional extent and internal structure of the gabbro. Direct observations of in situ subvertical igneous layering give confidence that most curvilinear [...]
Cretaceous tectonics and gold mineralisation in the Otago Schist, New Zealand
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
This paper provides a regional-scale background for understanding gold-mineralising processes in the Otago Schist during the Cretaceous. At this time the schist belt was in the latter stages of formation as an accretionary complex with 2000 km strike length on the Pacific margin of Gondwana. The Otago Schist is interpreted as an exhumed accretionary wedge of structurally stacked clastic [...]
Regional geological framework of New Zealands mineral deposits
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
New Zealand is the emergent part of a 4.9 Mkm2, mainly submerged continent in the SW Pacific Ocean that was formerly part of the Gondwana supercontinent. The geology can be described in terms of two main Cambrian-Early Cretaceous basement units (Western and Eastern provinces) and a Late Cretaceous-Holocene sedimentary and volcanic cover (Zealandia Megasequence and Rūaumoko Volcanics). New Zealand [...]
The 2018-2019 seismo-volcanic crisis east of Mayotte, Comoros islands: seismicity and ground deformation markers of an exceptional submarine eruption
Published: 2019-02-28
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
On May 10th, 2018, an unprecedented long and intense seismic crisis started offshore, east of Mayotte, the easternmost of the Comoros volcanic islands. The population felt hundreds of events. Over the course of one year, 32 earthquakes with magnitude greater than 5 occurred, including the largest event ever recorded in the Comoros (Mw = 5.9 on May 15th, 2018). Earthquakes are clustered in space [...]
Diagnosing spatial biases and uncertainties in global fire emissions inventories: Indonesia as regional case study
Published: 2019-02-28
Subjects: Environmental Monitoring, Environmental Sciences, Physical Sciences and Mathematics
Models of atmospheric composition rely on fire emissions inventories to reconstruct and project impacts of biomass burning on air quality, public health, climate, ecosystem dynamics, and land-atmosphere exchanges. Many such global inventories use satellite measurements of active fires and/or burned area from the Moderate Resolution Imaging Spectroradiometer (MODIS). However, differences across [...]
New insights on lake sediment DNA from the catchment: importance of taphonomic and analytical issues on the record quality
Published: 2019-02-27
Subjects: Earth Sciences, Ecology and Evolutionary Biology, Geochemistry, Geology, Life Sciences, Physical Sciences and Mathematics, Sedimentology, Soil Science, Terrestrial and Aquatic Ecology
Over the last decade, an increasing number of studies have used lake sediment DNA to trace past landscape changes, agricultural activities or human presence. However, the processes responsible for lake sediment formation might affect DNA archiving via taphonomic and analytical processes. It is crucial to understand these processes to ensure reliable interpretations for “palaeo” studies. Here, we [...]
Core Formation and Geophysical Properties of Mars
Published: 2019-02-25
Subjects: Earth Sciences, Geochemistry, Mineral Physics, Physical Sciences and Mathematics, Planetary Geophysics and Seismology, Planetary Sciences
The chemical and physical properties of the interiors of terrestrial planets are largely determined during their formation and differentiation. Modeling a planet’s formation provides important insights into the properties of its core and mantle, and conversely, knowledge of those properties may constrain formational narratives. Here, we present a multi-stage model of Martian core formation in [...]
Dynamics of the lithosphere and upper mantle in light of seismic anisotropy
Published: 2019-02-23
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Seismic anisotropy records continental dynamics in the crust and convective deformation in the mantle. Deciphering this archive holds huge promise for our understanding of the thermo-chemical evolution of our planet, but doing so is complicated by incomplete imaging and non-unique interpretations. Here, we focus on the upper mantle and review seismological and laboratory constraints as well as [...]
RSFit3000: A MATLAB GUI-Based Program for Determining Rate and State Frictional Parameters from Experimental Data
Published: 2019-02-22
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a MATLAB, graphical user interface (GUI) software package for analyzing rate and state friction experiments. Called RSFit3000, the software allows users to easily constrain frictional parameters by fitting velocity step and slide-hold-slide events using the aging and slip law forms for state variable evolution. RSFit3000 includes features for removing strain hardening/weakening trends [...]
Structural and geodynamic modelling of the influence of granite bodies during lithospheric extension: application to the Carboniferous basins of northern England
Published: 2019-02-22
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Intra-basinal highs within classic ‘block and basin’ style tectonic frameworks, in areas such as northern England, are underpinned by large granite bodies. This is widely believed to relate to the relative ‘rigidity’ and ‘buoyancy’ of granite in relation to accommodating basement. It has been suggested that during periods of tectonic extension, normal faulting around the peripheral regions of [...]